Mason Owners Alert: 30.9 spec'd in 31.6 frame!

This seems like a pretty big snafu, but one easily remedied.

I had started a thread about this, but have come up with more concrete info. The short of it: I had to warranty my first Mason frame due to a seat tube crack. VERY loose seatpost fitment. New frame arrived about a week ago. VERY loose post fitment, again.

So I decide to shim it. The frame/post ended up taking a homemade shim with 0.3mm wall thickness, meaning a 0.6mm difference in diameter. I then realized that this was only one tenth of a mm less than the shims used to fit 30.9 posts to 31.6 frames(0.7mm). I ordered up a 30.9 to 31.6 adapter shim from USE, and it fits nice and snug.

It seems some(maybe all???) Mason frames are coming with 31.6 tubing and 30.9 KS Dropzone dropper posts. This is a pretty big deal, since aluminum to aluminum post tolerance should ideally be < 0.05mm. The tolerance is 14 times too high. According to specs, this is SUPPOSED to be a 30.9 frame.

2 frames cannot be a coincidence. PLEASE check your Mason frames. They WILL crack if not shimmed, if incorrectly spec'd, as mine were. It's a ~10 dollar fix:

Had anyone contacted DB about this? Seems like a pretty big oversight if its leading to cracked frames.

I don't know. I was running a Spesh Command Blacklite, so they were initially skeptical about proper part sizing. After lots of pictures and measurements of both the new and original posts, they agreed to warranty the frame. At the time, I assumed it was a one off issue, and the suggestion was that the seat tube may have been honed excessively, causing the loose fitment.

After receiving the new frame, and realizing the same issue was present, I emailed the same contact that handled my frame warranty, notifying them of the issue in detail. I made it clear that I was not asking for anything, just passing along information. I have not heard back, nor am I interested in pursuing it further. What DB does with that info is up to them.

I can't, just CAN'T, be the only one with the issue. The two frames I received were shipped some 7 months or so apart, so the odds of that are beyond minuscule. I SUSPECT that there are others(hopefully few) out there riding similarly loose frames and won't realize unless/until they experience a failure. I never would have thought twice myself. I am about 200 pounds with gear, ride often, and somewhat aggressively. It took me a few months to develop(or at least notice) the crack.

I want to be clear that I have no ill will toward DB and I love the Mason HT. It's been a great bike, and I hope to ride it for a long time. My warranty only cost me two drives to the nearest dealer. I just want to warn other owners to check their frames, to avoid the hassle altogether.

Subscribed to see what happens to your new frame. I'm wondering if they aren't reaming the tube out to 31.6mm with that tool for who knows what reason, but that the post design is only for 30.9mm and that extra .7mm is the deal breaker in how much stress the tube will/can take. To me I'd guess they're using the wrong reaming tool/head, because being off by that much is not a small mistake as the OP said, that's a major snafu.